It is known in the art to provide highly complicated lock and access-preventing systems in buildings, rooms and automobiles which are closed by doors or other means so as to prevent the unauthorized access to such installations to prevent theft and other undesirable activities. The commonly used tumbler locks permit a large variety of key combinations, for example five thousand different combinations, which would normally make it extremely unlikely that the wrong key will accidentally open a lock for which it was not intended. Moreover, the installations, automobiles, buildings, etc. may then be separately secured by the installation of alarm systems which may signal any unauthorized entry or tampering which bypasses the lock/key system. These alarm installations are known in a large variety of designs and embodiments. Normally, these alarm systems are enabled or disabled separately from the operation which unlocks the mechanical lock on the doors, etc. For example, in motor vehicles, the removal of the ignition key and the closure of the driver's door may initiate a timed process which sets the alarm after a period of time has elapsed. In alarm systems used in buildings and the like, a separate key and lock system is normally used to set the alarm.
In spite of these precautions, it has been found, in fact, that even very complicated lock and key systems, for example the commonly used tumbler locks, cannot prevent unauthorized entry into the protected areas or unauthorized possession of secured objects. For example, the tumbler cylinder locks have often been defeated by the insertion of a deformable element which detects the pin configuration in the tumbler lock so that the person using this detector may have a duplicate key made which may be used immediately or at some opportune future time to gain access to the protected facility.
The alarm systems intended to protect the installation cannot afford protection against this type of circumvention because their existence is often known to the unauthorized party and they may be disabled rapidly. Even if they sound the alarm, which normally is a loud noise, the unauthorized party often will accept the risk of such an alarm. Yet again, the correct key may make it possible to turn off the alarm prior to its sounding. Similar considerations apply to various other localities and systems which protect buildings, rooms and objects by means of locks and the like. In the field of motor vehicles it has been shown by statistics that no apparent solution has been found for preventing the theft of, especially, expensive models of motor vehicles.
In alarm systems used in buildings and rooms which require the use of two separate keys, it is possible to insert the wrong key into the alarm system, causing the system to respond and sound a false alarm. If such false alarms occur with regularity, there is a tendency of the concerned person to become habituated to the occurrence of false alarms and this habit will tend to prevent a proper response in the event of a real alarm. All of these facts imply the need for an absolutely secure and trouble-free alarm system which can be set and disabled by the authorized party without concentrated attention and without triggering a false alarm.